1. Technical Field
The invention relates to a technique of suppressing deterioration of display quality when so-called phase-developed data signals are sampled.
2. Related Art
In recent years, projectors in which a small reduced image is formed using a display panel of liquid crystal or the like, and this small reduced image is enlarged and projected by an optical system have come into wide spread. The projectors themselves have no function to create images, and receive image data (or image signals) from host apparatuses, such as a personal computer and a television tuner. Since this image data which specifies the grayscale (brightness) of pixels is supplied in a format in which the pixels arrayed in a matrix is scanned vertically and horizontally, display panels used for the projectors also are appropriately driven according to this format. Therefore, the display panels used for the projectors generally are driven by a dot sequential method in which scanning lines are selected in a predetermined order one row by one row, data lines are selected sequentially one column by one column in a period in which one row of the scanning lines are selected, and data signals, which are obtained by converting image data so as to be suitable for driving of liquid crystal, are supplied to the selected data lines.
On the other hand, making display images high in definition have recently progressed like Hi-Visions. Although high definition display images can be achieved by increasing the number of rows of scanning lines, and the number of columns of data lines, frame frequency is fixed. Thus, one horizontal scanning period is shortened due to an increase in the number of rows of scanning lines, and a select period of data lines is also shortened in the dot sequential method due to an increase in the number of columns of data lines. Therefore, with the progression of high definition, the dot sequential method cannot sufficiently ensure the time taken to supply data signals to the data lines, which results in inadequate write-in to pixels.
Thus, a method called phase development driving has been invented for the purpose of canceling the inadequate write-in (refer to JP-A No. 2000-112437). This phase development driving is a method in which data lines are grouped for every predetermined columns, for example, every four columns (every six columns in JP-A No. 2000-112437), and are selected in a predetermined order by four columns in one horizontal scanning period, and data signals extended four times the length of the time axis are supplied to the selected four columns of data lines, respectively. Since this phase development driving method can ensure the time taken to supply data signals up to 4 times in this example as compared with the dot sequential method, it is considered suitable for high definition of display images.
Meanwhile, in such a phase development driving method, unevenness in the shape of a vertical stripe that the grayscales of pixels differ delicately every four columns of simultaneous selection is caused, and thereby deterioration of display quality becomes conspicuous.